1. Field of the Invention
The present invention relates to Time Division Multiple Access (TDMA) radio terminals and, in particular, to a method for stably displaying a battery voltage which temporarily varies during transmission and reception periods in a TDMA radio terminal.
2. Description of the Related Art
In general, a radio terminal such as a cordless telephone has a battery state displaying function for measuring a current battery voltage and displaying the battery state on a liquid crystal display (LCD). The battery state is generally displayed in the following increments so that a user may recognize the present battery state: a full battery state, a half battery state, a low battery state and an empty battery state.
FIGS. 1 and 2 are diagrams respectively illustrating variations of the current consumption and the battery voltage during transmission and reception periods in a TDMA radio terminal. As shown in FIG. 1, in a TDMA radio terminal such as a Digital European Cordless Telephone (DECT), current consumption abruptly increases during transmission (Tx) and reception (Rx). Correspondingly, the battery voltage also abruptly changes during transmission and reception, as shown in FIG. 2. Accordingly, it is difficult to stably display the battery voltage due to the continual variation of the battery voltage.
A conventional method for displaying battery voltage in a TDMA radio terminal will be described with respect to FIGS. 3 and 4. FIG. 3 is a diagram illustrating battery state areas in the conventional TDMA radio terminal, and FIG. 4 is a diagram illustrating a changing battery voltage with respect to a threshold level corresponding to two battery state areas. As shown in FIG. 3, the battery state is divided into four areas: a full battery state area, a half battery state area, a low battery state area and an empty battery state area. Conventionally, when the battery voltage exceeds a first threshold level (for the low battery state), the TDMA radio terminal displays the low battery state on the display, and when the battery voltage is lower than the first threshold level, the TDMA radio terminal displays the empty battery state. However, such a conventional method cannot stably display the battery state due to the continual variation of the battery voltage during the transmission and reception periods.
For example, assume that a battery voltage 411 changes during transmission and reception such that voltage 411 swings on (i.e., swings above and below) the first threshold level 412, as shown in FIG. 4. In such a case, the TDMA radio terminal displays the low battery state in an idle state and the empty battery state during transmission and reception due to the temporal change of the battery voltage. As a result, as transmission and reception are repeated at intervals, the terminal repeatedly changes the battery state, which decreases reliability of the battery state display function.
It is therefore an object of the present invention to provide a method for stably displaying a battery voltage which temporarily varies during transmission and reception periods in a TDMA radio terminal.
A method for displaying a battery voltage in a Time Division Multiple Access (TDMA) radio terminal is provided. The method includes the step of detecting the battery voltage. A battery state corresponding to one of a plurality of battery state areas is displayed, when the battery voltage corresponds to one of the plurality of battery state areas. On the other hand, a previous battery state is displayed, when the battery voltage corresponds to one of a plurality of buffer zones. Each of the plurality of buffer zones are disposed between two of the plurality of battery state areas. The battery state being currently displayed is then stored as a previous battery state.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.